Genetic manipulation of the mammalian visual system is currently limited by available tools for targeting gene knockout or overexpression to specific neuronal cell types, and is further hampered by an incomplete understanding of the normal gene expression in those cell types. This proposed studies will use a novel genetic strategy, lentiviral enhancer trapping, to generate new driver strains of mice expressing cre recombinase and tet activator in specific cell types. Recently developed cell type specific expression profiling will be used to map gene expression in these and other neurons within the central visual system. The genetic and genomic tools and resources developed will then be used to study the cellular and molecular mechanisms underlying experience dependent plasticity in layer 4 input neurons and layer 6 output neurons of the primary visual cortex.